barrow entropy

A campfire that doesn't go out all at once but smolders for hours because the wood inside still holds the heat of the past flame. That's roughly how the memory effect works for black holes. Normally, a tiny black hole with the mass of a mountain should evaporate in fractions of a second, scattering particles like sparks.

When you blow up a balloon too quickly, its surface starts to quiver. Something similar happened to space in the first moments after the Big Bang: the universe expanded rapidly, and the very fabric of space began to ripple.

Quantum field theory is the language physicists use to describe elementary particles and their interactions. The authors of the work decided to slightly "tweak" this language: they introduced deformations, that is, small changes to the rules of the game.

A whirlpool gulps down water, but splashes most of it back out. That's roughly how a black hole behaves when too much matter falls onto it. In a new study, astrophysicists ran 32 computer simulations to understand how a black hole's parameters — mass, spin, and "appetite"—control these cosmic fountains.

A stone falls into still water — ripples spread across the surface. A black hole behaves similarly when something falls into it or when it merges with another black hole. The hole begins to oscillate, and these oscillations propagate through space as gravitational waves.

A black hole sitting on a thin cosmic membrane (brane) resembles a heavy ball stretching an elastic sheet. In classical physics, it is bald — only mass, charge, and rotation. But add a scalar field (an invisible substance like temperature), and the hole can spontaneously grow 'fur' from this field.

Water turns to ice at zero degrees — sharply, with no intermediate states. Something similar happens to complexity when we take a random quantum state of an entire system and look only at a part of it. As long as that part occupies less than half the system, its complexity grows smoothly. But as soon as the fraction crosses 50%, a jump occurs.

A light ray skimming along a black hole horizon doesn't just move: it carries heat and information. Physicists have long suspected that the geometry of such rays obeys strict rules, but the details remained blurry. The new work turns these rules into a sharp inequality.

At the center of most galaxies lurk supermassive black holes — the overlords of gravity. Since 2019, thanks to interferometry with very long baselines, we’ve glimpsed their shadows: dark silhouettes set against a blazing gas backdrop. But what exactly is painting that shadow?

For a long time, cosmology was dominated by the belief, originating from Hawking: during the radiation era, primordial black holes do not grow.

An endless ocean where every wave carries information about what happens in the depths. That is roughly how our Universe works under the holographic principle: the physics inside a volume can be described by processes on its boundary.

Isolating the signal from a single pair of supermassive black holes is like hearing a dancer's footsteps amid the roar of a hurricane. Somewhere in space, these monsters spin in a slow gravitational tango, distorting spacetime itself.

Traditionally a black hole was described by three parameters — mass, charge, and angular momentum.

The hunt for non-Abelian anyons is a quest for a quantum ghost that leaves only one clue: entropy. These particles live in two-dimensional systems at ultralow temperatures. Their exchange doesn't just flip the sign of the wavefunction — it entangles states, creating topological order.

After the Big Bang, the universe underwent a rapid expansion — inflation, smoothing out the cosmic microwave background and sowing the seeds of galaxies. But at the quantum level, chaotic fluctuations brewed in the inflaton field.

At the center of galaxy M87, 55 million light-years away, lurks a black hole with a mass of 6.5 billion Suns. In 2019, the Event Horizon Telescope (EHT) gave us its first portrait: an orange donut with a dark core. But the donut is not the abyss itself.

In the first moments after the Big Bang, the universe was filled with a hot, nearly uniform plasma. But in some places, the density could randomly be slightly higher. If such a clump gained critical mass, it collapsed into a black hole: this is how primordial black holes were born.

In the search for the nature of dark matter, one of the most intriguing hypotheses traces back to the first moments after the Big Bang. Back then, quantum fluctuations of the inflation field gave rise to clumps of matter that could collapse into primordial black holes.

A supermassive black hole drifts through a cloud of dark matter. In the usual picture, this invisible substance just adds mass and barely interacts with ordinary matter. But dark matter particles could have intrinsic rotation — spin.

A black hole is not just a cosmic vacuum cleaner. It is a region with such strong gravity that even light cannot escape it. But place it in a perfect fluid of dark matter and add a cloud of strings, thin filaments stretched across all of space, and the picture gets more complicated.

A black hole is like a spinning top: the faster it spins, the more noticeable its behavior. It has two boundaries — the outer and inner horizons, the edges beyond which even light cannot return. In the new work, physicists looked inside a rotating charged black hole and multiplied the areas of these two surfaces.

A bonfire doesn't burn out all at once. If you glance at the flames at a random moment, all you see is a jumble of fire tongues, and you can never tell what exactly burned: a wet branch, an old magazine, or an armful of dry grass. But if you watch the fire hour after hour, rhythms emerge in its dance: a burst of heat, a lull, a change in color. These rhythms tell the story of what was thrown into the flames.

A swarm of tiny ice balls is scattered across a warm room. Some melt faster, others slower, but when only wet spots remain, they all vanish in the same way: the last drop evaporates according to the same law. This is roughly how primordial black holes behave — hypothetical objects born in the first moments after the big bang.

Black holes lose mass like water from a bucket in the sun — an evaporation discovered by Stephen Hawking.

Spacetime is like a giant sheet of paper. Fold it, and distant corners come together. Poke a pencil through, and you get a wormhole, a short tunnel through the folds. But the paper wants to spring back flat, snapping the passage shut. To keep it open, you need a rare “gasket”—matter with negative energy.

Light falling into a black hole carries information — for instance, the path a photon took. The horizon (the surface from which nothing returns) responds by changing its entropy — a measure of disorder, akin to the number of shuffled pages in a book.

Gravity isn’t fundamental: it’s a shadow cast by entropy, the measure of disorder. Back in the 1970s, Jacob Bekenstein and Stephen Hawking found that black holes store disorder on their surface, as if information is smeared across the shell.

A sugar cube weighs about a gram. But a black hole that could hide inside such a cube would weigh as much as a small mountain — billions of tons. Yet even such tiny things, born in the first instants after the Big Bang, should have vanished long ago.

A tiny black hole the size of an atomic nucleus but with the mass of a mountain emerged in the first moments after the Big Bang, when random clumps of energy collapsed into such objects.

Gravitational waves — ripples in spacetime predicted by Einstein — have exposed an abyss: black holes with masses between 60 and 120 solar masses are almost never born.

A black hole is not a frozen sphere. It's more like a soap bubble, whose walls can expand and contract. It even has two layers: the outer horizon, beyond which light cannot return, and the inner one, hidden deeper. When the hole swallows matter or loses energy, both layers shift, like the film of a bubble changing size.

Right after the Big Bang, the Universe expanded incredibly fast — this phase was called inflation. In some microscopic regions, matter randomly clumped so much that it collapsed into primordial black holes. They are tiny — the size of a proton, yet as massive as an iceberg.

In the first second after the Big Bang, the universe was a boiling cauldron of energy. Particle-antiparticle pairs were born and instantly annihilated each other. But for every billion such pairs, one particle of matter survived, and that leftover became stars, planets, and people. New research blames modified gravity for this.

A stone falls into a pond, and ripples spread across the water. Similarly, a black hole resting in the void may encounter a gravitational wave or a cloud of gas. It does not remain indifferent: its surface (the event horizon) bends slightly, like a stretched membrane under the weight of a drop.

A balloon is being inflated faster and faster. At first, it stretches smoothly, but at some point, the pump stutters — the speed drops, then picks up again. During this brief respite, tiny bubbles appear on the rubber. As inflation resumes, they turn into dense knots. Something similar happened to the universe itself right after the Big Bang.

The merger of two black holes is like a dance that ends in a powerful burst — a gravitational wave. This wave carries the imprint of how spacetime is curved around the objects. If the geometry differed from what we're used to, as if a ball rolled not on a flat floor but on wavy linoleum, the signal would be different.

Splitting water into hydrogen and oxygen with electricity is an age-old dream of clean fuel. But tiny gas bubbles stand in the way: they cling to the electrodes like foam on the side of a soda glass, interfering with the current's work. Each bubble is a tiny plug, blocking part of the surface where the reaction should occur.

Some black holes are remnants from the Big Bang. Usually they fade via a slow radiation leak — predicted by Stephen Hawking. But a quantum switch could invert them into white holes, explosively releasing all energy like popcorn kernels that suddenly pop.

Classical black holes, regions of spacetime with gravity so strong that even light cannot escape, according to general relativity, hide a singularity at their center: a point of infinite density and curvature where the known laws of physics break down.

Primordial black holes, hypothetical objects that emerged in the first instants after the Big Bang from the collapse of superdense fluctuations, should have vanished long ago according to Stephen Hawking's classic prediction: they would completely evaporate via quantum radiation, much like a puddle of…